Sprayable mining liner

ABSTRACT

A liner is the product of reaction of (a) a hydrophilic prepolymer bearing isocyanate groups; and (b) a water-borne polymer dispersion, the polymer bearing groups that are reactive to isocyanate groups; wherein the dispersion has a sufficiently high solids content, and the polymer has a sufficiently high modulus and glass transition or crystalline melting temperature, that the product of reaction exhibits a 24-hour Tensile Strength of at least about 2.5 MPa.

STATEMENT OF PRIORITY

This application is a divisional of application Ser. No. 10/236,541filed on Sep. 6, 2002 now U.S. Pat. No. 7,011,865 (and incorporatedherein by reference), which is a continuation-in-part of applicationSer. No. 09/952,150 filed on Sep. 11, 2001 now abandoned.

FIELD OF THE INVENTION

The invention relates to an elastomeric polymeric film that can be usedas a load-bearable coating, for example, to assist in protecting fromrock bursts in a mine. The invention also relates to a method forproviding support to surfaces such as, for example, rock surfaces.

BACKGROUND OF THE INVENTION

Underground mining requires support of the roof and walls of the mine toprevent injury due to rock bursts. Several materials have been used forthis purpose, including shotcrete, wire mesh, and sprayable linercompositions. Both shotcrete and wire mesh are somewhat difficult tohandle and apply in the underground mines, more particularly in deepmining applications. The application of shotcrete/gunite is laborintensive, and the linings are generally brittle, lacking in significanttensile strength and toughness, and prone to fracturing upon flexing ofthe rock during mine blasting. In addition, shotcrete/gunite generallydevelops its desired strength of about 1 MPa only slowly. The sprayableliners that develop strength quickly are often toxic during sprayapplication, whereas liners that have low toxicity during sprayapplication are often not tough enough and generally require more thanfour hours (at ambient temperature without application of heat) todevelop the minimum strength desired to be useful in the miningenvironment.

SUMMARY OF THE INVENTION

Thus, we recognize that a tough, flexible, easy-to-apply, quickstrength-developable (at ambient temperature) liner system is needed.The present invention provides such a liner, which is the product ofreaction of:

-   -   (a) a hydrophilic prepolymer bearing isocyanate groups; and    -   (b) a water-borne polymer dispersion, the polymer bearing groups        that are reactive to isocyanate groups;    -   wherein the dispersion has a sufficiently high solids content,        and the polymer has a sufficiently high modulus and glass        transition or crystalline melting temperature, that the product        of reaction exhibits a 24-hour Tensile Strength of at least        about 2.5 MPa.        Preferably, the polymer dispersion is a polyurethane dispersion.

As used herein, the term “liner” means a load-bearable coating that canbe applied to a surface (for example, the surfaces of mining cavities,highway overpasses and underpasses, and roadsides, for example, toprovide support and/or to contain loose or falling debris); the term“modulus” means tensile modulus and/or storage modulus; and the terms“24-hour Tensile Strength” and “4-hour Tensile Strength” mean a tensilestrength value that is measured 24 hours and 4 hours, respectively,after mixing components (a) and (b) according to ASTM D-638-97 (StandardTest Method for Tensile Properties of Plastics, published by AmericanSociety for Testing and Methods, West Conshohocken, Pa.) modified byutilizing a crosshead speed of 200 mm per minute, a sample width of0.635 cm (0.25 inch), and a gauge separation of 3.81 cm (1.5 inches).

The liner of the invention, in spite of its hydrogel nature, exhibitssurprising ultimate load-bearing capability (upon complete cure) and,prior to complete cure, generally develops sufficient strength to beuseful in a load-bearing capacity (for example in a mining environment)within 24 hours and, often, within about 4 hours. The starting linercomponents can be easily applied to a surface by spraying, yet cure toprovide a tough, flexible coating.

In another aspect, the invention provides a method for providing asurface with a liner, the method comprising

-   (a) applying to the surface    -   (1) a hydrophilic prepolymer bearing isocyanate groups, and    -   (2) a water-borne polymer dispersion, the polymer bearing groups        that are reactive to isocyanate groups; and-   (b) allowing the applied components (1) and (2) to react to form the    liner;    -   wherein the dispersion has a sufficiently high solids content,        and the polymer has a sufficiently high modulus and glass        transition or crystalline melting temperature, that the liner        exhibits a 24-hour Tensile Strength of at least about 2.5 MPa.

In yet another aspect, this invention also provides a kit for producinga liner, the kit comprising

-   -   (a) a hydrophilic prepolymer bearing isocyanate groups; and    -   (b) a water-borne polymer dispersion which when combined with        component        (a) reacts to form a liner, the polymer bearing groups that are        reactive to the isocyanate groups;    -   wherein the dispersion has a sufficiently high solids content,        and the polymer has a sufficiently high modulus and glass        transition or crystalline melting temperature, that the liner        exhibits a 24-hour Tensile Strength of at least about 2.5 MPa.

DETAILED DESCRIPTION OF THE INVENTION

Preferred polymer dispersions for use as component (b) or (2) are thosethat comprise polymers that are sufficiently stiff that a film preparedfrom the polymer (for example, by casting the polymer dispersion) has atensile modulus (measured according to ASTM D-638-97 (Standard TestMethod for Tensile Properties of Plastics, published by American Societyfor Testing and Methods, West Conshohocken, Pa.) modified by utilizing acrosshead speed of 245 mm per minute, a gauge separation of 51 mm, and asample thickness of 0.05 mm) of at least about 6.89 MPa at 100%elongation (more preferably at least about 13.79 MPa at 100% elongation,and most preferably at least about 20.69 MPa at 100% elongation) or astorage modulus of at least about 5×10⁸ dynes/cm² (more preferably, atleast about 1×10⁹ dynes/cm²) measured using a dynamic mechanicalanalyzer (DMA; for example, a Rheometrics™ RDA-2) at a sample thicknessof 1.5 mm and a frequency of 1 hertz in an 8-mm parallel plate at roomtemperature. More preferably, both the tensile modulus and the storagemodulus of the polymer fall within the respective preferred ranges.Preferred polymers have a glass transition temperature or crystallinemelting temperature (value of T_(g) or T_(m)) greater than about 30° C.,more preferably greater than about 40° C., most preferably greater thanabout 50° C.

Other preferred features of the polymer include (i) that it has amolecular weight (M_(w) in g/mol as measured by gel permeationchromatography (GPC) versus polystyrene standards) in the range of atleast about 50,000, more preferably from about 100,000 to about 700,000;(ii) that it is in the form of particles of an average size from about10 to about 10,000 nm, more preferably from about 30 to about 1000 nm,most preferably from about 30 to about 500 nm; and (iii) that thepolymer is used as a dispersion in water containing essentially noorganic solvent (for example, N-methylpyrrolidone). Surprisingly,dispersions of even high modulus, high T_(g) or T_(m) polymers can beused to obtain films (upon reaction with component (a)) without the needfor co-solvent (or added heat).

The groups on the polymer that are reactive to isocyanate groups arepreferably hydroxyl (alcohol), primary or secondary amino, or carboxylicacid groups, more preferably amino groups, most preferably primary aminogroups. Preferably, the polymer has an average reactive groupfunctionality of at least about one, more preferably at least about 2.

Polymer dispersions that can be used as component (b) includepolyurethane dispersions, poly(styrene-acrylic) dispersions, and thelike. Especially preferred are the polymer dispersions commonlyrepresented in the art by the term “polyurethane dispersions,” which isgenerally recognized (and used herein) to encompass such polymerdispersions as polyurea dispersions, polyurethane dispersions,polythiocarbamate dispersions, and dispersions of combinations thereof(for example, dispersions such as poly(urethane-urea) dispersions), aswell as dispersions of polyurethane-polyvinyl hybrids (preferably“copolymers” comprising semi-interpenetrating polymer networks)including, for example, polyurethane-polyacrylic dispersions. Thetypical waterborne polyurethane dispersion is often apoly(urethane-urea) dispersion due to reaction of some isocyanate withwater, followed by decarboxylation as described above, or due to chainextension by diamines. Most preferred are polyurethane-polyacrylicdispersions.

Water-borne polymers and processes for their preparation are known, andmany are commercially available. Examples of water-borne polyurethanesand such processes are described in “Advances in Urethane Science andTechnology”, Waterborne Polyurethanes; Rosthauser, James W.; Nachtkamp,Klaus; 1989, Vol. 10, pp. 121-162, Mobay Corp., Pittsburgh, Pa., thedescription of which is incorporated herein by reference. Thewater-borne polyurethane dispersion can be made, for example, accordingto one of the methods described in this reference. Other suitableexamples of water-borne polyurethane dispersions and processes for theirpreparation are described in U.S. Pat. Nos. 5,312,865; 5,555,686;5,696,291; 4,876,302, and 4,567,228. The disclosures of these patentsare incorporated herein by reference. A preferred method for forming thewater-borne polyurethane dispersion is the prepolymer method.Dispersions of polymers other than polyurethanes and processes for theirpreparation are described, for example, in Encyclopedia of PolymerScience and Engineering, Volume 6, pages 1-48, Wiley-Interscience, NewYork (1986), the description of which is incorporated herein byreference.

The water-borne polymer is preferably hydrophobic in nature to reduce orprevent hydrolysis of its polymeric backbone. The hydrolytic resistanceof the polymer can depend on the backbone of the precursor (for example,in the case of a polyurethane, the polyol) that is used in itssynthesis. Useful precursor polyols include, for example, polyetherpolyols, polyester polyols, polycarbonate polyols, and the like.Normally adipic acid-based polyester polyols are more resistant tohydrolysis than phthalate-based polyester polyols. The polyurethanedispersions made from prepolymers having polyols based on polycarbonateor dimer acid diol generally have higher hydrolytic resistance thanpolyester-based polyols.

Suitable non-urethane water-borne dispersions include Acronal™ 305D, awater-based styrene-acrylic emulsion (total solids 50%) available fromBASF, USA. Suitable water-borne polyurethanes include, for example,NeoPac™ 9699, a water-borne urethane/acrylic based polyurethane (totalsolids 40%; viscosity 100 cps at 25° C.; elongation 160%; 100% modulus26.2 MPa) from Neoresins, Ontario, Canada; Hauthane™ HD 2334, apolyether water-borne urethane dispersion (solids 45%; elongation 200%;100% modulus 17.24 MPa) from C. L. Hauthaway & Sons Corporation, MA,USA; Hybridur™ 580, a polyester-acrylic based urethane dispersion fromAir Products, USA; and Hybridur™ 580, an acrylic-urethane dispersion,from Air Products & Chemicals Inc., PA, USA.

The amount of water present in these commercially available dispersionsranges from about 35% or 50% to about 65% or 70% by weight. This rangeis normally satisfactory for use in the invention. Use of amounts ofwater outside of this range are, however, within the scope of thisinvention, and the percentage of water can be readily adjusted.Generally, water-borne polymer dispersions useful as component (b) or(2) will have a solids content (content of solid polymer) of at leastabout 30 percent by weight (preferably, at least about 35 percent byweight; more preferably, at least about 40 percent by weight; mostpreferably, at least about 50 percent by weight) based upon the totalweight of the dispersion. Preferably, the dispersion contains no morethan about 80 percent (more preferably, no more than about 70 percent;most preferably, no more than about 60 percent) water by weight, basedupon the total weight of the dispersion.

Other water-borne polymeric emulsions (such as emulsions of variousacrylic, styrene butadiene, or vinyl acetate polymers) that form acontinuous liner film of lower tensile strength (than the valuesdescribed above for component (b) or (2) polymers) can replace part ofthe water-borne polymer dispersion. Examples include Rhoplex™ 2848 andRhoplex™ 2438 (acrylic emulsions from Rohm & Haas Company). However,these emulsions generally reduce the initial (4 hrs) and ultimatetensile strengths and generally cannot provide the desired preferredstrength of the resulting liner of at least about 1 MPa tensile strengthwithin about 4 hours at room temperature, preferably within about twohours.

Hydrophilic isocyanate group-bearing prepolymers suitable for use in theliner, kit, and method of the invention are those that are capable ofreacting with component (b) (or (2)) to form a crosslinked hydrogel. Oneclass of useful prepolymers is that represented by the formula:R[(R′O)_(a)—C(O)NH—R″(NCO)_(b)]_(c)wherein R is an active hydrogen-free residue of a polyol (preferably, apolyether polyol, for example, ethylene glycol, glycerol, or1,1,1-trimethylolpropane); (R′O)_(a) is a hydrophilic poly(oxyalkylene)chain having a plurality of randomly distributed oxyethylene and higheroxyalkylene units; the subscript “a” (the number of oxyalkylene units inthe poly(oxyalkylene) chain, this number being sufficient to impartwater-solubility and preferably noncrystallinity to the prepolymer) hasa value between about 50 and about 500; R″ is a residue or nucleus of apolyisocyanate precursor (preferably an aromatic nucleus, for example,toluene); “b” is an integer, generally 1-5, where (b+1) is the number ofisocyanate moieties present in the polyisocyanate precursor; thesubscript “c” is a number equal to the functionality or number of activehydrogen atoms in the polyol, and generally “c” will be 2-6. The moiety—C(O)NH— together with the adjacent oxygen atom of the poly(oxyalkylene)chain is a carbamate (or urethane) group resulting from the reaction ofa hydroxy group of the polyol precursor with an isocyanate moiety fromthe polyisocyanate precursor. The terminating isocyanate groups canreact with water, resulting in the formation of a gelled mass.

Preferred hydrophilic prepolymers are those of the formula:R[(CH₂CH₂O)_(d)(CH(CH₃)CH₂O)_(e)(CH₂CH₂O)_(f)—C(═O)NH—R″—NCO]_(c)where R, R″, and “c” are as defined above, and “d”, “e” and “f” areintegers such that the ratio of (d+f):e is 2:1 to 4:1.

The hydrophilic prepolymer is preferably a urethane-containing polymerbearing isocyanate groups and can be formed by reacting a hydrophilicpolyol with an excess of monomeric polyisocyanate. This step can befollowed by purifying the hydrophilic prepolymer of unreacted monomericpolyisocyanate or, preferably, by quenching the unreacted monomericpolyisocyanate with a compound that is reactive to isocyanate groups, sothat the prepolymer preferably contains less than about 0.7 weightpercent (more preferably, less than about 0.5 weight percent) ofunreacted monomeric polyisocyanate.

Unless the amount of unreacted monomeric polyisocyanate present in themixture containing the hydrophilic prepolymer is lowered through apurification step or effectively reduced by, for example, quenching theisocyanate groups of the monomeric polyisocyanate, the presence of themonomeric polyisocyanate can result in toxicity (for example, duringspraying). It was surprisingly found that by removing or quenching theunreacted monomeric polyisocyanates according to a preferred process ofthe present specification, preferred liners of superior strength wereproduced. Other advantages include reduced toxicity, and lowered heatgeneration.

The hydrophilic prepolymer can be purified from unreacted monomericpolyisocyanate by processes and/or methods using, for example, fallingfilm evaporators, wiped film evaporators, distillation techniques,various solvents, molecular sieves, or organic reactive reagent such asbenzyl alcohol. U.S. Pat. No. 4,061,662 removes unreacted tolylenediisocyanate (TDI) from an isocyanate prepolymer by contacting theprepolymer with molecular sieves. U.S. Pat. Nos. 3,248,372, 3,384,624,and 3,883,577 describe processes related to removing free isocyanatemonomers from prepolymers by solvent extraction techniques. It is alsopossible to distill an isocyanate prepolymer to remove the unreacteddiisocyanate according to U.S. Pat. No. 4,385,171. It is necessary touse a compound that is only partially miscible with the prepolymer andhas a higher boiling point than that of the diisocyanate to be removed.U.S. Pat. Nos. 3,183,112, 4,683,279, 5,051,152 and 5,202,001 describefalling film and/or wiped film evaporation. According to U.S. Pat. No.5,502,001, the residual TDI content can be reduced to less than 0.1 wt.% by passing the prepolymer at ˜100° C. through a wiped film evaporator,while adding an inert gas, especially nitrogen, to the distillationprocess to sweep out the TDI. The method descriptions of all of thesereferences are incorporated herein by reference.

In a preferred purification method, unreacted preferably monomericpolyisocyanates can be quenched with an amine (preferably a secondaryamine, more preferably a monofunctional secondary amine) or an alcohol(for example, an arylalkyl alcohol), preferably in the presence of atertiary amine catalyst (such as, triethylamine) or an alkoxysilanebearing a functional group that is reactive to isocyanate groups (forexample, an amine). The unreacted polyisocyanates are more preferablyreacted with an arylalkyl alcohol, such as benzyl alcohol, used with atertiary amine. The unreacted polyisocyanates are most preferablyreacted with an arylalkyl alcohol, such as benzyl alcohol, used inconjunction with an alkoxysilane bearing one secondary amino group. Theunreacted polyisocyanates can be quenched without substantiallyaffecting the terminal isocyanate groups of the hydrophilic prepolymer.

Examples of suitable amines include N-alkyl aniline (for example,N-methyl or N-ethyl aniline and its derivatives), diisopropylamine,dicyclohexylamine, dibenzylamine, and diethylhexylamine.

Example of suitable alcohols include arylalkyl alcohols (for example,benzyl alcohol and alkyl-substituted derivatives thereof).

Examples of suitable silanes include Dynasylan™ 1189(N-(n-butyl)-aminopropyltrimethoxysilane available from DegussaCorporation, NJ, USA), Dynasylan™ 1110(N-methyl-3-aminopropyltrimethoxysilane available from DegussaCorporation, NJ, USA), Silquest™ A-1170 (bis(trimethoxysilylpropyl)amine available from Osi Specialties, CromptonCorporation, USA), and Silquest™ Y-9669(N-phenyl)-gamma-aminopropyltrimethoxysilane available from OsiSpecialties, Crompton Corporation, USA).

When alcohols are used to quench the unreacted polyisocyanates, theapplication of heat is often required to reduce the reaction time.Reactions with amines can generally be conducted, however, at ambienttemperature for a relatively shorter period of time.

The amount of unreacted monomeric polyisocyanate present in the reactionmixture comprising the hydrophilic prepolymer following the reactionwith the amine, alcohol, or silane is most preferably 0, but preferablycan range up to about 0.7 weight percent, more preferably up to about0.5 weight percent.

A preferred method of purifying the hydrophilic prepolymer (a) is by themethod of U.S. patent application Ser. No. 09/952,118, filed on evendate herewith, the disclosure of which is incorporated herein byreference.

A suitable, relatively low-cost hydrophilic polyol for use in thepreparation of the hydrophilic prepolymer bearing isocyanate groups is apolyether polyol having at least two, preferably three, hydroxyl groups,and a number average molecular weight in the range of from about 2,000to about 20,000, preferably about 2,000 to about 5,000, most preferablyabout 4,000 to about 5,000, and having random ethylene oxide units andhigher alkylene oxide units in a mol ratio of ethylene oxide (EO) tohigher alkylene oxide of 1:1 to 4:1. The higher alkylene oxide can beselected from the group consisting of propylene oxide (PO), butyleneoxide, pentylene oxide, hexylene oxide and mixtures thereof. Thehydrophilic polyol is preferably a polyoxyethylene-propylene polyolcomprising, for example, 50 to 70% EO and 30 to 50% PO. A particularlypreferred polyether triol is one comprising approximately 68% EO andapproximately 32% PO. Alternate ratios of EO:PO can be used in preparingthe hydrophilic polyol of the present invention provided that thehydrophilicity of the resulting polyol is not significantly adverselyaffected. These ratios can be determined by routine testing.

Commercially available polyol precursors useful in making the abovedescribed water-soluble isocyanate-terminated prepolymers arehydrophilic polyether polyols, for example, a polyG™ triol, such as“polyG™-83-84” (30% ethylene oxide and 70% propylene oxide), availablefrom Arch Chemicals. The degree of overall hydrophilicity of theprepolymeric mixtures can be modified by varying the ratio of ethyleneoxide to propylene oxide in the hydrophilic polyol, or by using smallamounts of poly(oxyethylene-oxypropylene) polyols sold under thetrademark “Pluronic”, such as Pluronic-L35, F38, and P46, or hydrophilicpolyols with heteric oxyethylene-oxypropylene chain sold by HuntsmanPerformance Chemicals, Utah, USA, as Polyol Functional Fluids, such asWL-580, WL-600, and WL-1400.

The hydrophilic prepolymer bearing isocyanate groups can be prepared,for example, by reacting a polyisocyanate with a copolymer ofpolyoxyethylene-propylene polyol using an NCO/OH equivalent ratio ofabout 5:1 to about 1.05:1, preferably a ratio of about 2.0:1 to 2.5:1.The preparation of isocyanate-terminated prepolymers is disclosed in,for instance, U.S. Pat. Nos. 4,315,703 and 4,476,276 and in referencesmentioned in those patents. The disclosures of these patents areincorporated herein by reference. Preferably, aromatic isocyanate isused for its greater reactivity rate than aliphatic isocyanate. Benzoylchloride can be added during prepolymer preparation to avoid sidereactions of polyisocyanate.

Polyisocyanates that can be used to prepare the hydrophilic prepolymerhaving isocyanate groups include aliphatic and aromatic polyisocyanates.The preferred polyisocyanates are aromatic polyisocyanates. One of themost useful polyisocyanate compounds that can be used is tolylenediisocyanate, particularly as a blend of 80 weight percent oftolylene-2,4-isocyanate and 20 weight percent oftolylene-2,6-isocyanate; a 65:35 blend of the 2,4- and 2,6-isomers isalso useable. These polyisocyanates are commercially available under thetrademark “Hylene”, as Nacconate™ 80, and as Mondur™ RD-80. The tolyleneisocyanates can also be used as a mixture with methylene diisocyanate.Other polyisocyanate compounds that can be used include other isomers oftolylene diisocyanate, hexamethylene-1,6-diisocyanate,diphenyl-methane-4,4′-diisocyanate, m- or p-phenylene diisocyanate, and1,5-naphthalene diisocyanate. Polymeric polyisocyanates can also beused, such as polymethylene polyphenyl polyisocyanates, such as thosesold under the trademarks “Mondur” MRS, and “PAPI”. A list of usefulcommercially available polyisocyanates is found in Encyclopedia ofChemical Technology by Kirk and Othmer, 2nd Ed., Vol. 12, pages 46-47,Interscience Pub. (1967).

Preferably, no solvent is used to dilute the hydrophilic prepolymer.However, a solvent can be used if necessary. Solvents that can be usedto dissolve the prepolymer are water-miscible, polar organic solventsthat are preferably volatile at the ambient conditions of theenvironment where the composition is to be used. The solvent chosenshould be such that the resulting solution of prepolymers and solventwill not freeze at the ambient conditions present in the environmentwhere the mixed composition of the invention is to be applied. Forexample, where the ambient temperature is about 50° F., a solution ofabout 60-90 (or higher) weight percent of prepolymer solids in dryacetone is an effective composition. Other useful water-misciblesolvents include methyl acetate, tetrahydrofuran, monoethyl etheracetate (sold under the trade designation “Cellosolve” acetate), diethylacetal, and hydrophilic plasticizers, such as Atpol™ 1120 polyether,available from Uniquema, Belgium.

The product of the reaction of hydrophilic prepolymer and the polymerdispersion is a gelatinous mass, as the hydrophilic moieties of thehydrophilic prepolymer absorb water that is the vehicle of the polymer.This gelatinous mass is sometimes referred to as a gel or hydrogel, andit can be used, for example, as a liner in a mine. Reaction times toconvert the prepolymer to the gel can be on the order of less than aminute to several hours.

By utilizing a sufficiently high solids content dispersion comprisingpolymer having a sufficiently high modulus and glass transition orcrystalline melting temperature, the formed gel generally develops aminimum strength of at least about 2.5 MPa within about 24 hours (and,preferably, a minimum strength of at least about 1 MPa within about fourhours, more preferably within about 2-4 hours). The solids content ofthe dispersion and the modulus and glass transition or crystallinemelting temperature of the polymer can be varied over a wide range, andthe skilled artisan will recognize that a high value for one or two ofthese parameters can be selected so as to compensate for a low value(for example, a value outside of the preferred ranges described above)of another. The tensile strength of the liner after it is completelyformed (fully cured) is preferably at least about 6-12 MPa, morepreferably at least about 10-12 MPa, at room temperature. (When “cured,”the product of reaction of components (a) and (b) has generally lostmost of its water content (for example, more than about 90 percent) andcrosslinking is essentially completed.) When the liner-producingcomponents of the present invention are applied at colder temperaturesor under high humidity conditions, longer periods of time can berequired for the liner to become fully cured. Tensile strength build-upcan be accelerated, if desired, by the application of heat during andafter application of the components (for example, to accelerate the rateof water evaporation and crosslinking).

When component (b) (or (2)) contains at least about 30% by weight ofsolid polymer, the weight ratio of component (a) (or (1)) to component(b) (or (2)) is preferably in the range of about 1:3 to about 1:10, morepreferably from about 1:4 to about 1:7, and most preferably from about1:5 to about 1:6, but, when component (b) (or (2)) has a higher solidscontent than about 50% by weight, the ratio can be 1:1. However, toincrease the hydrophobicity of the resulting liner it is desirable andpreferred to use as little of component (a) as possible.

Some of the isocyanate groups of the hydrophilic prepolymer can reactwith water to form carbamic acid moieties which immediatelydecarboxylate to generate amines. These amines can then react with otherisocyanate groups to lead to crosslinking of the prepolymer. Water canbe absorbed into the ethylene oxide matrix of the product leading toformation of a gel. The liner of the present invention is preferablygas-tight and flexible. The liner of the invention preferably has anelongation at break of from about 100 to about 1000%, more preferablyfrom about 100 to about 800%, even more preferably from about 100 toabout 400%, most preferably from about 100 to about 300%. The resultingliner is, therefore, preferably, a water-insoluble, cross-linked,water-containing gelatinous mass having a high degree of flexibility.

The liners produced according to the invention can be used asload-bearable coatings to support, for example, rock surfaces in a mine.For such applications, the liners are preferably thick, around 0.5 mm to6 mm, when cured completely and after removal of aqueous solvent.

Other additive ingredients can be included in the liner of the presentinvention. For example, viscosity modifiers can be included to increaseor decrease the viscosity, depending on the desired applicationtechnique. Fungicides can be added to prolong the life of the gel and toprevent attack by various fungi. Other active ingredients can be addedfor various purposes, such as substances to prevent encroachment ofplant roots, and the like. Other additives that can be included in theliner of this invention, include, without limitation, rheologicaladditives, fillers, fire retardants, defoamers, and coloring matters.Care should be exercised in choosing fillers and other additives toavoid any materials that will have a deleterious effect on theviscosity, the reaction time, the stability of the liner being prepared,and the mechanical strength of the resulting liner.

The additional filler materials that can be included in the liner of thepresent invention can provide a more shrink-resistant, substantiallyincompressible, and fire retardant liner. Any of a number of fillercompositions have been found to be particularly effective. Usefulfillers include water-insoluble particulate filler material having aparticle size of about less than 500 microns, preferably about 1 to 50microns, and a specific gravity in the range of about 0.1 to 4.0,preferably about 1.0 to 3.0. The filler content of the cured liner ofthe present invention can be as much as about 10 parts filler per 100parts by weight cured liner, preferably about 5 parts to about 10 partsper 100.

Examples of useful fillers for this invention include expandablegraphite such as Grafguard™ 220-80B or Grafguard™ 160-150B (Graftech,Ohio, USA); silica such as quartz, glass beads, glass bubbles, and glassfibers; silicates such as talc, clays, (montmorillonite) feldspar, mica,calcium silicate, calcium metasilicate, sodium aluminosilicate, andsodium silicate; metal sulfates such as calcium sulfate, barium sulfate,sodium sulfate, aluminum sodium sulfate, and aluminum sulfate; gypsum;vermiculite; wood flour; aluminum trihydrate; carbon black; aluminumoxide; titanium dioxide; cryolite; chiolite; and metal sulfites such ascalcium sulfite. Preferred fillers are expandable graphite, feldspar,and quartz. The filler is most preferably expandable graphite. Theamount of filler added to the liner of the invention should generally bechosen so that there is no significant effect on elongation or tensilestrength of the resulting liner. Such amounts can be determined byroutine investigation.

When filler is utilized, the resulting liner can also be fire retardant.For some applications, the liner preferably should meet the fireretardant specifications of CAN/ULC-S102-M88 or ASTM E-84. These testsdetermine burn rate and the amount of smoke generation.

The starting components (a) (or (1)) and (b) (or (2)) of the liner ofthe invention are preferably mixed immediately before being applied to asurface. As an example of the mixing process, components (a) and (b) canbe pumped using positive displacement pumps and then mixed in a staticmixer before being sprayed onto a surface. The mixture of the twocomponents can then be sprayed onto a substrate with or without airpressure. The mixture is preferably sprayed without the use of air. Theefficiency of mixing depends on the length of the static mixer. Usefulapplication equipment includes, for example, a pump manufactured byGusmer Canada, Ontario, Canada, as Model H-20/35, having a 2-partproportioning high pressure spray system that feeds through a heatedtemperature controlled (for example, 50° C.) zone to an air purgingimpingement mixing spray head gun of, for example, type GAP (Gusmer AirPurge) also manufactured by Gusmer.

Objects and advantages of this invention are further illustrated by thefollowing examples, but the particular materials and amounts thereofrecited in these examples, as well as other conditions and details,should not be construed to unduly limit this invention.

EXAMPLES

Test Methods:

Test method ASTM D-638-97 (Standard Test Method for Tensile Propertiesof Plastics, published by American Society for Testing and Methods, WestConshohocken, Pa.), modified by utilizing a crosshead speed of 200 mmper minute, a sample width of 0.635 cm (0.25 inch), and a gaugeseparation of 3.81 cm (1.5 inches), was used for measuring tensilestrength and elongation. The tests were performed using an Instron Model44R1122 tensile tester. Storage modulus was measured using a dynamicmechanical analyzer (a Rheometrics™ RDA-2) at a sample thickness of 1.5mm and a frequency of 1 hertz in an 8-mm parallel plate at roomtemperature.

Liners that were made in accordance with the present invention havepassed the Dynamic Stress Membrane Materials testing. Small-scale testsconfirmed that the lining material met the basic requirements set byboth the liner manufacturer and members of the mining industry. Forsmall scale testing, the liner material was applied by hand mixingcomponents (a) and (b) of the liner composition to the surface ofgranite core samples (2 inches (5.1 cm) in diameter and 4 inches (10.2cm) long) leaving a 6 mm gap at each end. A leading mining companysupplied the granite cylinders. A crush test was carried out at GolderAssociates, in London, Ontario, after the samples were left for 4 hoursand 24 hours at room temperature. Force was applied on the cylinders bya compressive load using a soft, uncontrolled testing machine tomaximize the potential energy available to sustain a violent type offailure of the cylinders. The granite cylinders were failed withoutdamaging the applied liner on the cylinders.

Large granite cylinders (7.5 inch (about 19 cm) in diameter and 19 inch(about 48 cm) long) were sprayed using a pump system and mixed in astatic mixer with two different liner compositions using three differentthicknesses. These tests were carried out in Sudbury, Ontario in CANMETLab. Again, the cylinders were crushed without affecting the appliedliners.

Prepolymer 1:

A general description of prepolymer preparations that can be used toprepare prepolymer A is given in U.S. Pat. No. 4,476,276, the disclosureof which is incorporated by reference, especially the preparation ofprepolymers A, B and C of U.S. Pat. No. 4,476,276.

An amount of benzoyl chloride 0.04% (based on the total amount of polyoland tolylene diisocyanate (TDI)) was blended at room temperature underan inert atmosphere with 1 equivalent of polyether triol (a copolymer ofethylene oxide and propylene oxide sold under the trade designationpolyG-83-34, mol. wt. 5400, available from Arch Chemicals), thereafter,2.4 equivalents of an 80:20 mixture of 2,4 tolylene diisocyanate: 2,6tolylene diisocyanate (Mondur™ TD-80 available from Bayer Corporation,USA) was added to the resultant mixture with agitation, producing amoderate exotherm that was maintained at 80-85° C. until the reactionwas completed. The solution of the prepolymer was then cooled to roomtemperature. The solution contained prepolymers having on average 3.0 to3.2 weight percent isocyanate groups, and 1.2-2.4 weight percentmonomeric TDI, as determined by nuclear magnetic resonance (NMR)techniques.

Prepolymer 2:

In a 3-necked 2 L round bottom flask, equipped with a mechanical stirrerand a thermometer, 1271.3 g of Prepolymer 1 was added under an argonatmosphere, 98.1 g (30 molar percent with respect to the total NCOgroups in Prepolymer 1) of Silquest™ A-1170 bis(trimethoxysilylpropyl)amine (available from Osi Co.) was added dropwiseto the prepolymer at 25° C. under argon and with stirring (250 rpm). Thereaction was exothermic causing a 0-10° C. increase in temperature. Thereaction mixture was collected after 2 h. The monomeric TDI content wasfound to be below 0.5 weight percent, as determined by NMR.

Prepolymer 3:

In a 3-necked 250 ml round bottom flask, equipped with a mechanicalstirrer and a thermometer, 205.9 g of Prepolymer 1 were added underargon. 7.52 g (40 molar percent with respect to the total NCO groups inPrepolymer 1) of N-ethyl aniline was then added to the prepolymer whilestirring at 25° C. The mixture was collected after 2 h. The monomericTDI content was found to be below 0.2 weight percent, as determined byNMR.

Prepolymer 4:

In a 3-neck round bottom flask, equipped with a mechanical stirrer and athermometer, 200 g of Prepolymer 1 was added under argon. 2.74 g (15molar percent with respect to the total NCO groups in Prepolymer 1) ofN-ethyl aniline was added dropwise to the prepolymer at 25° C. underargon and with stirring (250 rpm). The reaction was kept at roomtemperature for 2 h. Then 7.52 g (15 molar percent with respect to thetotal NCO groups in the Prepolymer #1) Silquest™ A-1170 bis(trimethoxysilylpropyl)amine was added to the mixture under argon andwith stirring. The reaction was kept at room temperature for 2 h beforecollection. The monomeric TDI content was found to be below 0.3 weightpercent, as determined by NMR.

Prepolymer 5:

In a 3-neck 250 ml round bottom flask, equipped with a mechanicalstirrer and a thermometer, 201.0 g of Prepolymer 1 was added underargon. 2.45 g (15 molar percent with respect to the total NCO groups inPrepolymer 1) of benzyl alcohol was added to the prepolymer under argon.The temperature was then raised to 85° C. and the reaction was carriedout for 2 h. After the reaction mixture was cooled to room temperature,7.52 g (15 molar percent with respect to the total NCO groups inPrepolymer 1) Silquest™ A-1170 bis (trimethoxysilylpropyl)amine wasadded to the mixture under argon and with stirring. The reaction waskept at room temperature for 2 h before collection. The monomeric TDIcontent was found to be below 0.2 weight percent, as determined by NMR.

Prepolymer 6:

In a 3-necked 2 L round bottom flask, equipped with a mechanical stirrerand a thermometer, 1280.0 g of Prepolymer 1 and 320.0 g of dry acetonewere added under argon atmosphere. 134.8 g (40 molar percent withrespect to the total NCO groups in the prepolymer of Example 1) ofSilquest™ A-1170 bis (trimethoxysilylpropyl)amine was added dropwise tothe solution at 25° C. under argon and with stirring (900 rpm). Thereaction mixture was collected after 2 h. The monomeric TDI content wasfound to be below 0.1 weight percent, as determined by NMR.

Prepolymer 7:

In a 3-necked 500 ml round bottom flask, equipped with a mechanicalstirrer and a thermometer, 374.9 g of Prepolymer 1 was added under anargon atmosphere. 17.36 g (17 molar percent with respect to the totalNCO groups in Prepolymer 1) of Silquest™ A-1170bis(trimethoxysilylpropyl)amine (available from Osi Co.) was addeddropwise to the prepolymer at 25° C. under argon and with stirring (250rpm). The reaction was exothermic, causing a 0-10° C. increase intemperature. The resulting mixture was allowed to react for 1 hour atambient temperature and then heated at 45° C. for 2 hours. The reactionmixture was collected after that period. The monomeric TDI content wasfound to be below 0.7 weight percent, as determined by NMR.

TABLE A Component (b) Polymer Characteristics Glass Transition orTensile Percent N- Crystalline Modulus Storage Methyl Melting at 100%Modulus Isocyanate- Polymer Dispersion Percent Pyrrolidone TemperatureElongation (dynes/ Reactive (Component (b)) Solids (NMP) (° C.)+ (MPa)cm²) Groups Vancryl ™ 937 46 0 24 — — no Luphen ™ 3528 40 7 <35  7.5* —no Acronal ™ 305D 50 0 36 — 5 × 10⁹ yes Hybridur ™-580 40 7 80 — 3 × 10⁹yes Hauthane ™ 45 0 — 17**  — yes HD-2334 NeoPac ™ R- 40 0 >80 26**  3 ×10⁹ yes 9699 +measured using a dynamic mechanical analyzer (DMA) exceptfor the value for Vancryl ™ 937, which was supplied by the manufacturer*measured at a cross head speed of 200 mm/min, cross sectional area ofsample 0.17 mm², and gauge 20 mm **measured as described on page 3 above— data not available

Examples 1-5

Examples 1-5 provide data for liners formed using NeoPac™ 9699polyurethane dispersion and different prepolymers. The samples were madeby quickly injecting 4.0 g of a prepolymer to 20 g of NeoPac™ 9699 (40%)solid polyurethane dispersion (from NeoResin Canada) followed by mixingthe two components with a spatula and spreading the mixture on apolyester film to a thickness of about 2 to 3 mm. The film surface wasnot smooth due to rapid gelling of the two components. The value oftensile strength of these samples, and the components used to producethem are provided in Table 1. The results indicate that prepolymers witha low amount of monomeric diisocyanate (except for Example 3, which isquenched with 40 molar percent mono-functional amine) can provide thesame or better tensile strength as compared to Example 1, a liner formedby unmodified prepolymer and polyurethane dispersion. Although Example 3does not demonstrate a tensile strength of 1 MPa after 4 hours, it doesdemonstrate good results after three days.

TABLE 1 Tensile properties Tensile properties at 4 h at 3 days ExamplePrepolymer Strength Elongation Strength Elongation No. No. (MPa) (%)(MPa) (%) 1 1 1.3 305 9.1 550 2 2 1.2*  840* 10.2 330 3 3 0.9 800 10.2330 4 4 1.6 630 9.2 350 5 5 1.7 660 8.9 380 *Value at 3 hr.

Comparative Examples 1 and 2 and Examples 6-8

The samples of the following examples and comparative examples were madeby injecting 4.5 g of prepolymer quickly to 20 g of each dispersionalong with 2 g of fused silica, mixing with a spatula and spreading on apolyester film to a thickness of 1.9 mm to 3 mm. The films were not verysmooth due to rapid gelling of the two components. The values of tensilestrength of these samples, and the components used to produce them areprovided in Table 2.

TABLE 2 Tensile Strength Example Components of Amount (MPa) No.Composition (g) After 4 hours C-1 Prepolymer 6 (A) 4.5 0.34 Vancryl ™937 (B) 16.8 Fused Silica 2.0 C-2 Prepolymer 6 (A) 4.5 0.44 Luphen ™3528 (B) 20 Fused Silica 2.0 6 Prepolymer 6 (A) 4.5 1.12 Hauthane ™HD-2334 (B) 18.0 Fused Silica 2.0 7 Prepolymer 6 (A) 4.5 2.08 NeoPac ™R-9699 (B) 20 Fused Silica 2.0 8 Prepolymer 6 (A) 4.5 1.23 Hybridur ™580 (B) 20 Fused Silica 2.0 Vancryl ™ 937 is a 46% solidsstyrene-acrylic based emulsion (having no isocyanate-reactive groups)available from Air Products, USA. Luphen ™ 3528 is a 40% solidspolyurethane dispersion (having no isocyanate-reactive groups) fromBASF, USA. Hauthane ™ HD-2334 is a 45% solids polyether-basedpolyurethane dispersion from Hauthaway & Sons Corporation. NeoPac ™R-9699 is a 40% solids polyester-polyacrylic based polyurethaneco-polymer, available from Neo Resins Canada. Hybridur ™ 580 is a 40%solids polyester-polyacrylic based polyurethane co-polymer, availablefrom Air Products, USA.

Example 9

Liners were made by spraying component A (Prepolymer 6) which containsless than 0.1 weight percent of free TDI and component B (NeoPac™R-9699) at a weight ratio of 1:5 with 2 separate pumps and mixingcomponents A & B in a static mixer. The compositions formed were smoothand showed higher tensile values compared to hand mixed samples. Theresulting hand-made and pump-sprayed films were then tested after 4hours to determine their tensile strengths. The strengths were alsoevaluated after 3 days and after several weeks. The results are shown inTable 3.

TABLE 3 4 hr.* 1 day* 2 days* 7 days* 7 days** Tensile Strength 1.8 9.410.9 12 15 (MPa) % Elongation 700 406 310 252 225 *Samples were left atambient temperature **Samples were left at 50° C. for 2 days and then 1day at RT.

Example 10

A test was conducted in which a control gel containing no fireretardants and samples containing several different fire retardants wereignited with an open flame. A sample prepared from 4 g of Prepolymer 1or 2, 20 g of component NeoPac™ 9699 and 0.25-1.0 g of the expandablegraphite Grafguard™ 220-80B (Graftech, Ohio, USA) showedself-extinguishability. A sample prepared with the expandable graphiteGrafguard™ 160-150B also demonstrated self-extinguishability but to alower extent.

Examples 11-14

The samples of the following examples were made by mixing 50 g ofprepolymer quickly with 200 g of each dispersion using a hand-heldcartridge attached to a static mixer (3M™ Mix PAC, type Dp 200-70/0499)and injecting into a stainless steel mold that was coated withfluoropolymer film (available from 3M, St. Paul, Minn., USA as 3M™Scotch™ 5490 tape) to a thickness of 3 mm. The films were smooth andtranslucent. The values of tensile strength of these samples, and thecomponents used to produce them are provided in Tables 5 and 4,respectively.

TABLE 4 Tensile Strength Example Components of Amount (MPa) No.Composition (g) After 4 hours 11 Prepolymer 7 (A) 5 3.3 Acronal ™ 305 D(B) 20 12 Prepolymer 7 (A) 5 2.2 NeoPac ™ 9699 (B) 20 13 Prepolymer 7(A) 5 2.4 Acronal ™ 305 D (B) 10 NeoPac ™ 9699 (B) 10 14 Prepolymer 7(A) 5 4.7 NeoPac ™ 9050 (B) 20 Acronal ™ 305 D is a 50% solidacrylic-styrene based emulsion available from BASF, USA. NeoPac ™ 9699and NeoPac ™ 9050 contain the same polyester-polyacrylic basedpolyurethane co-polymer, available from Neo Resins Canada, but havesolids contents of 40% and 50%, respectively.

TABLE 5 Tensile Strength (MPa) Example No. 4 hr. 1 day 3 days 5 days**11 3.3 4.8 7 7 12 2.2 6.6 12 16 13 2.4 — 7.8 10 14 4.7 9.5 11.2 13**Samples were left at 50° C.

Various modifications and alterations to this invention will becomeapparent to those skilled in the art without departing from the scopeand spirit of this invention. It should be understood that thisinvention is not intended to be unduly limited by the illustrativeembodiments and examples set forth herein and that such examples andembodiments are presented by way of example only with the scope of theinvention intended to be limited only by the claims set forth herein asfollows.

1. A mine opening lined with a liner comprising the product of reactionof: (a) a hydrophilic prepolymer bearing isocyanate groups that arecapable of reacting with water to form a gelled mass; and (b) awater-borne polymer dispersion, said polymer bearing groups that arereactive to said isocyanate groups.
 2. A mine opening lined with a linercomprising the product of reaction of: (a) a hydrophilic prepolymerbearing isocyanate groups that are capable of reacting with water toform a gelled mass; and (b) a water-borne polymer dispersion, saidpolymer bearing groups that are reactive to said isocyanate groups;wherein said dispersion has a sufficiently high solids content, and saidpolymer has a sufficiently high modulus and glass transition orcrystalline melting temperature, that said product of reaction exhibitsa 24-hour Tensile Strength of at least about 2.5 MPa.
 3. A mine openinglined with a liner comprising the product of reaction of: (a) ahydrophilic prepolymer bearing isocyanate groups; and (b) a water-bornepolyurethane-polyacrylic or poly(styrene-acrylic) dispersion, saidpolyurethane-polyacrylic or poly(styrene-acrylic) bearing groups thatare reactive to said isocyanate groups.
 4. A mine opening lined with aliner comprising the product of reaction of: (a) a hydrophilicprepolymer bearing isocyanate groups that are capable of reacting withwater to form a gelled mass; and (b) a water-borne polymer dispersion,said polymer bearing groups that are reactive to said isocyanate groups;wherein said dispersion has a water content no greater than about 80percent by weight, based upon the total weight of said dispersion.
 5. Akit for producing a liner, said kit comprising (a) a hydrophilicprepolymer bearing isocyanate groups that are capable of reacting withwater to form a gelled mass; and (b) a water-borne polymer dispersionwhich when combined with said component (a) reacts to form a liner, saidpolymer bearing groups that are reactive to said isocyanate groups;wherein said dispersion has a sufficiently high solids content, and saidpolymer has a sufficiently high modulus and glass transition orcrystalline melting temperature, that said liner exhibits a 24-hourTensile Strength of at least about 2.5 MPa.
 6. A kit according to claim5, wherein said polymer used in component (b) has a molecular weight inthe range of at least about 50,000.
 7. A kit according to claim 5,wherein said polymer of component (b) is in the form of particles of asize from about 10 to about 10,000 nm.
 8. A kit according to claim 5,wherein said dispersion has a solids content of at least about 30percent by weight, based upon the total weight of said dispersion.
 9. Akit according to claim 5, wherein a film prepared from said polymer usedin component (b) has a tensile modulus of at least about 6.89 MPa at100% elongation.
 10. A kit according to claim 5, wherein a film preparedfrom said polymer used in component (b) has a value of T_(g) or T_(m)greater than about 30° C.
 11. A kit according to claim 5, wherein saiddispersion contains no co-solvent.
 12. A kit according to claim 5,wherein said liner exhibits a 4-hour Tensile Strength of at least about1 MPa.
 13. A kit according to claim 5, wherein said prepolymer is formedby reacting a polymer bearing hydroxyl groups with a monomericpolyisocyanate to form a urethane-containing polymer bearing isocyanategroups, which is purified by removing unreacted monomeric polyisocyanateor by quenching unreacted monomeric polyisocyanate with a compound thatis reactive to isocyanate groups.
 14. A kit according to claim 5,wherein said polymer dispersion is selected from the group consisting ofpolyurethane dispersions and poly(styrene-acrylic) dispersions.
 15. Akit according to claim 14, wherein said polymer dispersion is apolyurethane dispersion.
 16. A kit according to claim 15, wherein saidpolyurethane dispersion is a polyurethane-polyacrylic dispersion.
 17. Akit according to claim 5, wherein said polymer dispersion is inadmixture with a dispersion of an acrylic polymer, a styrene-butadienecopolymer, or a vinyl acetate polymer.
 18. A kit according to claim 5,wherein the weight ratio of component (a) to component (b) is in therange of about 1:3 to about 1:10.
 19. The kit of claim 5, wherein saidliner has a thickness in the range of from about 0.5 mm to about 6 mm.20. The kit of claim 5, wherein said prepolymer is derived from at leastone polyether polyol.
 21. The kit of claim 20, wherein said polyetherpolyol is trifunctional.
 22. The kit of claim 5, wherein said groupsthat are reactive to said isocyanate groups are amino groups.
 23. A kitfor producing a liner, said kit comprising (a) a hydrophilic prepolymerbearing isocyanate groups; and (b) a water-bornepolyurethane-polyacrylic or poly(styrene-acrylic) dispersion which whencombined with said component (a) reacts to form a liner, saidpolyurethane-polyacrylic or poly(styrene-acrylic) bearing groups thatare reactive to said isocyanate groups.
 24. A kit according to claim 23,wherein said kit further comprises expandable graphite.
 25. A kitaccording to claim 23, wherein said prepolymer is derived from at leastone polyether polyol and said isocyanate groups are derived from atleast one aromatic polyisocyanate.
 26. A kit according to claim 23,wherein said dispersion is a polyurethane-polyacrylic dispersion.
 27. Akit for producing a liner, said kit comprising (a) a hydrophilicprepolymer bearing isocyanate groups that are capable of reacting withwater to form a gelled mass; and (b) a water-borne polymer dispersionwhich when combined with said component (a) reacts to form a liner, saidpolymer bearing groups that are reactive to said isocyanate groups;wherein said dispersion has a water content no greater than about 80percent by weight, based upon the total weight of said dispersion.
 28. Akit for producing a liner, said kit comprising (a) a hydrophilicprepolymer bearing isocyanate groups that are capable of reacting withwater to form a gelled mass; and (b) a water-borne polymer dispersionwhich when combined with said component (a) reacts to form a liner, saidpolymer bearing groups that are reactive to said isocyanate groups;wherein said dispersion has a sufficiently high solids content, and saidpolymer has a sufficiently high modulus and glass transition orcrystalline melting temperature, that said liner exhibits a 4-hourTensile Strength of at least about 1 MPa.